NORTHWOOD - While no one was injured, an elderly couple must stay with their son after a chimney fire spread into the walls of their home Monday morning.

Police firefighters and emergency personnel responded to 51 Old Dump Road at 10:29 a.m. after the residents smelled a burning odor and smoke singed their eyes, which caused them to leave the home.

.The fire spread from the chimney to the nearby wall, which forced firefighters to open up the side of the home and disable the lines to the home's oil heater. As a result, the home is uninhabitable during the cold temperatures...Fire Lt. Dave Wakeman said firefighters from Northwood were assisted by crews from Deerfield, Epsom, Nottingham, Pittsfield and Strafford.

Wakeman said it's important to clean chimneys, furnaces and fireplaces before cold weather sets in...'The rule of thumb is twice a year,' Wakeman said, adding he recommends cleaning chimneys before the cold sets in and half-way through the winter.

Wakeman said chimney fires are caused by a build-up of creosote, a natural by-product of burning wood, which funnels the heat and can be dangerous...He said residents should take notice when there is a sharp increase in temperatures around the stove pipe or if they hear a crackling sound in the wall.

'With a free burning fire, it sounds like a train going by,' Wakeman said, adding by this time, residents should evacuate the home and call firefighters...'It's better to err on the side of caution,' Wakeman said.